The present invention relates to a game machine and an information storage medium for displaying a two-dimensional image obtained through the perspective projection conversion of a three-dimensional virtual space as looked from a predetermined visual point position.
Conventionally, a game has been well known in which a character (called a “player character”) manipulated by the player is moved in a game space that is a three-dimensional virtual space to make an adventure while clearing a number of events occurring on the course. This kind of game, which is generally referred to as a role playing game, proceeds in such a way that the player character solves a given problem at a particular place, and throws down an enemy character arising on the course. In particular recently, along with the higher performance of processors and the development of image processing techniques, a method of representing the player character, the enemy character or the background by a three-dimensional object with the polygon is generally used.
In displaying an image within the game space on the screen, a perspective projection conversion process is performed by setting the visual point position at a predetermined location within the game space, and a two-dimensional image obtained through this conversion process is displayed.
By the way, in the conventional game machine in which the player character is represented by the three-dimensional object, a two-dimensional image is displayed in the game space as observed from the visual point position set at the predetermined location. Hence, if there is an obstruction between this visual point position and the player character, the player character disappears. Thereby, there was a problem of impairing the operability by the player.
To cope with this problem, various techniques have been known as disclosed in Japanese Patent Laid-Open Nos. 7-85312, 9-50541, and Japanese Patent No. 2902352. In a three-dimensional dynamic image creating apparatus as disclosed in Japanese Patent Laid-Open No. 7-85312, a camera position (visual point position) is automatically shifted to a position at which a subject corresponding to the player character can be seen. Also, in a virtual image generating apparatus as disclosed in Japanese Patent Laid-Open No. 9-50541 or a video game machine as disclosed in Japanese Patent No. 2902352, a transmission process for the obstruction is performed.
However, if any of the methods as disclosed in these patents is employed, the shift of visual point position or the transmission process is automatically performed when the player character is hidden behind the obstruction. Therefore, in the case where the player character is hidden behind the obstruction only in a moment, the visual point may be shifted, although the player can issue an operation command in a current state. Hence, there is a problem of rather impairing the operability and making it difficult to grasp the display contents. For example, in the case where the player character is hidden behind the obstruction only in a moment and then appears again as it is moved to an observable position, the visual point position should not be changed to grasp the movement direction of the player character and increase the operability. Also, in the case where the player character is hidden behind the obstruction in a moment and appears again repeatedly and alternately many times, the transmission process for the obstruction is repeated many times, resulting in a risk of making the display contents obscure.